POWER AMPLIFIER
4000
FEATURES
◆
2x1300 W into 8
Ω
2x2100 W into 4
Ω
2x2400 W into 2
Ω
at clip level with two
channels driven
◆
Compact design, 2 U high
(88 mm)
◆
Low weight
◆
MLS™ switches for each channel
offers power matching into
different loads without increased
power losses
◆
Electronically balanced
inputs
◆
LED indicators show
output voltage and
headroom
◆
Output cooled by Intercooler
®
◆
Two proportional speed fans
◆
Independent protection circuitry
◆
Short circuit protection
manages long-term short-circuit
operations
◆
DC protection
◆
Clip limiter
◆
VHF protection
◆
AFS™-limiter
The LAB 4000 is a compact (2 unit
high) light-weight (10 kg) power
amplifier designed for high quality
touring sound systems and fixed
installations.
The chassis is made of 2 mm black
anodised aluminium, with a 4 mm
thick front panel. The switch-mode
power supply is placed just behind the
front panel to ensure noise free
operation. Both the power supply and
the two output channels are cooled by
two proportional speed fans with
airflow from front to back.
The switch-mode power supply is
the modern solution of the weight and
size problem. With switch technology
operating at a high frequency, it is
possible to use ferrite transformers
instead of heavy iron transformers and
large electrolytic capacitors.
Switch-mode technology has been
applied in power supplies in TV-sets
during the latest 30 years. But in the
LAB 4000 the power capacitivity is 20
times larger.
We have designed the LAB 4000 to
obtain the same characteristics as a
conventional power supply. Thanks to
the switch-mode power supply it is
easy to get the DC-rail voltage
stabilised. This is made by controlling
the magnetic energy in the ferrite
transformer with a pulse width
processor and magnetic “Flux Sense”
windings.
The LAB 4000 has an upgraded
version of the well known switch mode
output stage from the LAB 2000. The
power transistors are cooled by a solid
copper cooler, called Intercooler(r),
originally designed for our LAB 1300
power amplifier. Lab.gruppen’s specially
designed thermal feedback circuit
protects against thermal breakdown.
Short circuit protection;
The LAB 4000 is completely short-
circuit protected -even in reactive loads.
The LAB 4000 is equipped with
Lab.gruppen’s specially designed short-
circuit protection, which permits very
high peak-currents,, but still holds the
transistors within the so-called “Safe
Operation Area” at the present
operating voltage. This makes it possible
to run loudspeakers with impedance
variations, which are considerably lower
than the lowest permitted impedance of
the power amplifier.
Six more protection circuits, which
are separate for each channel, protect
the LAB 4000 and the loudspeakers:
DC protection; There are two types of
D.C. protection; Fuses on the supply
branches of each channel (this is an
IEC 65 requirement) and a Crowbar
bar protection that shorts the output.
Thermal protection; Protects the
amplifier from over heating and
causing damage to the output stages.
The indicators come on before the
signal is muted.
Clip limiter; Prevents severely clipped
waveforms from reaching the loud
speakers, but maintains full peak power.
As a by product, when the amplifier
comes out of a protect condition, the
output level has a slow rise time. The
effect is like turning the gain up slowly.
VHF(Very high frequency)
protection; Protects the loudspeaker
against non-musical signals outside the
audible area.
AC protection; shuts down the outputs
if the line voltage is outside the
operating voltage of the LAB 4000.
AFStm-limiter; Adaptive Fuse Saver,
limits the mains current to a safe level
according to the time lag of an 16
ampere slow blow fuse.
All electronics are mounted on four
modules. The modules are easily
accessible for replacement or repair, etc.
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